Pressure induced phase transitions in GaSe-, TlGaSe2- and CdGa2S4-type crystals

All overview is given of recent, experimental results on the structural and optical properties of layered GaSe-, TlGaSe2-, and defect, chalcopyrite. CdGa2S4-type, semiconductors under hydrostatic pressure. Emphasis is made on pressure induced phase transitions. Perspectives for future research are considered in this article, which does not pretend to be one reflecting all existing papers on discussed subjects.